Elementalist's Palette is a rare Artifact card from Secrets of Strixhaven Commander (SOC), collector number 346. Current market price: $0.30, TCGplayer market prices via Scryfall.
Whenever you cast a spell with {X} in its mana cost, put two charge counters on this artifact. {T}: Add one mana of any color. {T}: Add {C} for each charge counter on this artifact. Spend this mana only on costs that contain {X}.